The invention relates to a circuit arrangement for the time-dependent monitoring of the state prevailing on lines, comprising a device in which, in the event of a change in state on a line, a line address which identifies the line and a state criterion which indicates the change in state are formed.
In order to allow state changes on lines, for example, on connection lines or data lines connected to an exchange, to be recognized a circuit arrangement has been proposed in U.S. Pat. No. 3,576,399 (see also German published application No. OS 26 41 913), wherein the lines, combined to form groups, are interrogated in accordance with the so-called "last-look" process and those lines which exhibit changes in state are identified. As a result of such an interrogation, criteria are available regarding the change in state and the line addresses of those lines upon which the state changes have occurred. In addition to recognizing the change in state and identifying the relevant line, in many cases it is necessary to carry out a time-dependent monitoring of the changes in state. Call recognition may be mentioned as an example. This is to be understood in that a change in state which signals a change from a stipulated reset state to a stipulated call state cannot be evaluated as call criterion until the expiration of a predetermined length of time. Short term changes in state resulting from interference influences are thus suppressed.